1. Field of the Invention
This invention relates to waterjet pumps and is particularly directed to means for eliminating the need for an axial thrust control seal for waterjet pumps.
2. Description of the Prior Art
In waterjet pumps of the prior art, it has been customary to provide a seal to reduce axial thrust of the rotor against the aft bearings. Unfortunately, these seals have been highly susceptable to erosion by sand and the like with the result that the eroded seals have caused increased loads on the aft bearings, causing rapid deterioration of the aft bearings and increased maintenance for the pump.
Another problem of prior art waterjet pumps has been the fact that the action of the pump in driving the water has induced a helical motion in the pump discharge which tends to push the boat off course. To overcome this problem, it is common to provide flow straightening vanes aft of the rotor drum to straighten the discharge flow from the pump. The vane designs of the prior art have overcome the helical motion of the pump discharge, but have tended to increase the axial thrust load of the rotor drum and, hence, have increased seal erosion and bearing failure.